1. Field of the Invention
The invention relates to solid, water-soluble salt mixtures consisting of micronutrients and stabilizers, to processes for their preparation and to their use in an aqueous solution for providing cultivated plants with microelement nutrients, especially through leaf dressing.
2. Brief Description of the Prior Art
Water-soluble microelement fertilizers have hitherto been known in solid (e.g., German Pat. No. 23 13 921) or in liquid form, especially as aqueous solutions (e.g., German Unexamined Application 24 34 875) or European Unexamined Application 0006411) or in pasty form (e.g., German Published Application 28 46 832).
These micronutrient concentrates are generally diluted with water or dissolved in it prior to use.
In the case of pasty micronutrient concentrates, handling, under certain circumstances, is unsatisfactory.
The liquid micronutrient fertilizers have the disadvantage that they contain large quantitites of diluents, especially water. This makes handling difficult and results in unnecessary packaging and shipping costs. Occasionally, precipitation occurs during storage.
Therefore, complex-forming compounds, especially chelating agents, are usually added to keep the micronutrients in solution in the concentrates and their solutions. (Cf., e.g., Volumn 2 "Boden und Dungemittel" (Soil and Fertilizers) second half, pp 1352-1354 of the handbook "Pflanzenernahrung und Dungung" (Plant Nutrition and Fertilization) published by H. Linser, Springer Verlag, Vienna, New York, 1968).
The compounds of this group of materials are used as the free acids, as well as their salts, especially the alkalis.
Although the compositions are generally formulated so that only a portion of the amount required for the complete complexing of the cations present is used, for example, "at least 20% of the bivalent and trivalent cations present in the mixture, but preferably 40%" and more (Cf. German Pat. No. 23 13 921, column 3, lines 15-20 and Table of Examples 1 to 7 in columns 3/4, especially the last line) or at least 25% (according to German Published Application 28 46 832, column 1, line 8), avoiding the use of such large quantities appears desirable, since chemical compounds with complexing properties could present problems, for instance, through activation of heavy metals in the soil. Furthermore, the addition of the complexing agents in large amounts is expensive.
Therefore, in accordance with German Published Application 28 46 832, only that quantity of complexing agent is used which is required to complex at least 25% of the trace element cations present, with 2 to 18 weight percent of polyethylene glycol ether derivatives being added. General economic and environmental considerations also recommend a most frugal application of the polyethylene ether derivatives.
Therefore a need has continued to exist for a micronutrient composition which overcomes the drawbacks of the known micronutrient concentrates.